(1) Field of the Invention
The present invention relates to the field of communication networks. Specifically, the present invention relates to the field of identifying and correcting for communication faults within the communication paths of an overall network system arraigned in a token ring typology.
(2) Prior Art
Communication networks provide capability for multiple computer systems, peripherals and other information storage, retrieval or processing units (stations) to share data between themselves over the communication network. There are various network topologies that a communication network can adopt which are old in the art of communication networks; these topologies include star topology, tree topology (or generalized bus topology) and token ring topology. In a token ring topology, units or nodes of the communication network are communicatively interconnected in a close-end ring fashion with each node occupying a particular position within the overall ring structure. Several nodes on a particular ring may physically reside on a network concentrator which provides, among other control functions, a coupling platform for the associated nodes (stations). Each network concentrator of a Token Ring network also contains a network management module or NMM which performs several control and timing functions between the associated nodes of the token ring network and intercommunication between the nodes.
Within the token ring communication network, in order for one node to communicate with another node in the network it must have priority to a unique token dataframe or code which traverses the ring. This token travels around the nodes of the ring until one particular node requests communication. The node requesting communication will take the token from the ring and transmit a signal that the token is busy. At that point none of the other nodes may communicate over the ring because the token has been replaced with a busy token or marked busy. The node with the token, the source node, may then transmit a message package to another particular node, the destination node. The message package (dataframe) will indicate the destination node by a particular label attached to the message or dataframe. The message is passed along the nodes of the ring structure in a particular direction, node by node, until the destination node receives the message. After the destination node receives the message, it copies the message into its internal buffer and also continues to send the message along the ring until the source node receives the message back. Once the source node receives its own message it then releases the token back onto the ring and discontinues the message. A network management module attached to the ring may also remove messages that have traversed the ring more than once, i.e., if the source module faulted after sending the message.
In a token ring structure each node is called a repeater because each node repeats a message through the ring whether or not the particular message is destined for that node. Therefore, the communications scheme of a ring topology communication network requires that each and every node of the ring be operating properly to repeat messages around the ring. A disastrous effect will occur within a token ring if one particular node or station malfunctions and will not repeat messages. A faulting station will break the communication line that point. This occurrence will bring the entire token ring network down since messages will not flow past the malfunctioning node. In this state, problem stations can also prevent new stations from being inserted into the network and can disconnect or interrupt higher logical session layers (i.e., SNA).
Several reasons may cause a node along the token ring to malfunction. First, a node having an incorrect communication frequency may be inserted into the token ring network. The incompatible frequency will lock out the newly added node from the network. Or, a cable may break in between stations of the ring network thus breaking the ring at one or more places. If adjacent stations become physically isolated then the network will fail. Also a station may malfunction and not remove itself from the ring causing a break in the communication network. In any of a number of different scenarios, it would be advantageous to be able to detect a malfunctioning node and remove or isolate that node from the remainder of the network to prevent communication failure. The present invention offers such a solution.
A way to identify and isolate malfunctioning stations within the token ring system is to pull out the cables associated with each station until the malfunctioning station is removed. However this solution is not practical in large complicated network systems. Moreover, what is needed is a system that can automatically isolate the problem station without requiring user interaction. The present invention offers such capability. Also, the IEEE 802.5 communication standard provides a system for beacon removal within a communication network to prevent network shutdown. However, if the malfunctioning or problem station does not conform the 802.5 standard then the malfunctioning station will not be removed from the ring network. What is needed is a system for identifying and isolating problem stations that do not conform to a particular standardized communication protocol. The present invention provides such a system.
Therefore, it is an object of the present invention to advantageously improve communication reliability and integrity within a token ring communication network. It is further an object of the present invention to identify a malfunctioning station within the communication ring and communicatively isolate (bypass) that malfunctioning station from the remainder of the token ring communication network to prevent network shutdown. It is also an object of the present invention to accomplish the above objects within the framework of existing token ring communication networks without the need for substantial additional hardware. It is an object of the present invention to provide the above features in an automatic system and among nodes that may or may not conform to a particular predetermined communication protocol. These and other objects of the present invention not specifically mentioned above will be evident from the detailed descriptions of the present invention herein presented.
The above mentioned IEEE 802.5 communication standard provides a general overview and background of the well-known token ring communication typology. For this reason, the IEEE 802.5 standard protocol is incorporated herein by reference.